Trenchers are machines used for digging trenches into which pipe, cable and the like may be laid and then covered. The trench cut by the trencher is as cleanly formed as possible to reduce unnecessary damage to the earth surface since such trenches are commonly make to lay underground wiring or telephone cables in residential areas.
Such trenchers commonly have the trenching head or cutting tool mounted on the rear of the vehicle with the filling blade mounted on the forward end. The operator faces forwardly and while the machine is moving in the forward direction, the trenching head is lowered and the trench is dug. After the trench is completed or simultaneously therewith, the cable or pipe is laid in the trench. Thereafter, the filling blade on the forward end of the trencher is used to fill the trench with the previously removed earth.
Present trenchers suffer many disadvantages. One problem is the operators position. Because the operator faces forwardly, he is continually looking rearwardly over his shoulder to determine the operating characteristics of the trenching head. When a trench is being dug, however, there is considerable shock transferred to the vehicle and thereafter transferred to the operator. When the operator is in a position with his head sidewise to observe the trenching unit, there is additional strain placed on his back and the additional shock because of such an operating position results in frequent spinal injuries to such operators.
A further problem with existinq trenchers is that relating to the operating platform and controls. In present trenchers, foot operated controls for at least some of the trencher functions are present. The presence of such foot operated controls on the operating platform creates tripping opportunities and a cluttered operating environment. More importantly, however, the chance of a back injury occurring is increased. This is so because the operator may place additional strain on his back because of the concurrent use of a foot control when his sight extends rearwardly in observing the trenching head. Some trenchers have rotatable operating consoles. When the operating console is rotated, the presence of foot operated controls or other obstructions on the operating platform of the trencher offer the potential for inconvenience and possible injury to the operator when the operating console is being rotated.
Yet a further problem with existing trenchers is that most are mechanically operated or utilize a combination of mechanical and hydraulic components to power the vehicle and to operate the trenching unit attached to the vehicle. Mechanical components in a trencher, while being commonly used and easily available are not the most desirable components in a machine which is continually subject to shock and impact loading. This is so since, again, the impact loads are transmitted directly to the frame of the vehicle and, thereafter, are transmitted to the operator. Such loads are absorbed only minimally in the mechanical components used for the power train and trenching unit. A related problem is that with a mechanical power train using forward and rearward differentials, the position of the drive shaft from the prime mover to the rear differential results in an operator straddling the drive shaft. Again, therefore, the operating platform is obtrusive and inconvenient for the operator.
Yet a further problem relates to the frame of existing trenchers. Usually, such trenchers have a longitudinal frame with series of cross members located transversely between the longitudinal frame members. The hydraulic fluid and fuel oil tanks are mounted in a position attempted to be non-obtrusive but they serve only the function of carrying fuel or hydraulic fluid. The use of the tanks strictly for a single function increases the weight of the trencher and the cost unnecessarily.
Yet a further problem with existing trenchers has been the serviceability of components which must be inspected and serviced frequently. Such components are generally located between the frame members which makes access difficult.
Yet a further problem with existing trenchers again relates to the operators use of the machine. Such problems as the line of sight which extends from the operating position to the ends of the filling blade and, as well, which should extend to the entire trenching unit have never been satisfactorily resolved.
Yet a further problem with existing trenchers lies in the use of their axle assemblies and filling blades. In order to obtain a properly floating filling blade, it is advantageous to have a support arm for the blade as long and as nearly horizontal as possible. Such a design allows a blade to more smoothly transfer loading forces because the moment created by such forces on the filling blade will be minimized. Present trenchers use four wheel drive designs with a drive shaft connected between forward and rearward located differentials. Such differentials are large and decrease ground clearance which is undesirable. More importantly, the presence of a differential and drive shaft in the forward and lower area of the trencher will prohibit the support arm extending from the filling blade from proceeding below the differential because of the aforementioned ground clearance objective. Thus, more complex and costly designs must be used to obtain a satisfactorily floating filling blade.
Yet a further problem with existing trenchers relates to the use of the trenching unit itself. Mechanically driven trenching units are used with drive shafts and drive gears. Because such trenching units are pivotable from the transport to the operating position only about the axis of the drive gear, the trenching unit position is necessarily a compromise between the two positions. In addition, the transverse position of the trenching unit with a mechanical drive can only be changed with considerable difficulty.
Yet a further problem relating to present trenching units is that impacts caused by hard rocks, tree roots and the like contacting the teeth attached to the digging chain are transmitted to the trenching unit itself and the power source for the trenching unit. This is a particular problem when hydraulic motors are used as the prime movers for the trenching unit as such impacts cause pressure spikes which can damage the hydraulic motor and driving pump